Automated Flow Lines in Production and Operation Management

An automated flow line consists of several machines or workstations which are linked together by work handling devices that transfer parts between the stations. The transfer of work parts occurs automatically and the workstations carry out their specialized functions automatically. The flow line can be symbolized as shown in Fig. 10.2. A raw workpart enters one end of the line and the processing steps are performed sequentially as the part moves from one station to the next. It is possible to incorporate buffer zones into the flow line, either at a single location or between every workstation. It is also possible to include inspection stations in the line to automatically perform intermediate checks on the quality of the workparts. Manual stations might also be located along the flow line to perform certain operations which are difficult or uneconomical to automate.

Automated flow lines are generally the most appropriate means of productions in cases of relatively stable product life; high product demand, which requires high rates of production; and where the alternative method of manufacture would invoice large labour content.

The objectives of the use of flow line automation are:

1. To reduce labour costs;
2. To increase production rates;
3. To reduce work-in-process;
4. To minimize distances moved between operations;
5. To achieve specialization of operations; and
6. To achieve integration of operations.

There are two general forms that the workflow can take. These two configurations are in­line and rotary.

In-line Type

The in-line configuration consists of a sequence of workstations in a more-or-less straight line arrangement. The flow of work can take a few 90° turns, either for workpiece reorientation, factory layout limitations, or other reasons, and still qualify as a straight-line configuration. A common pattern of workflow, for example, is a rectangular shape, which would allow the same operator to load the starting workpiece and unload the finished workpiece.

Rotary Type

In the rotary configuration, the workparts are indexed around a circular table or dial. The workstations are stationary and usually located around the outside periphery of the dial. The parts ride on the rotating table and are registered or positioned, in turn, at each station for its processing or assembly operation. This type of equipment is often referred to as an indexing machine or dial index machine and the configurations.

The choice between the two types of configurations depends on the application. The rotary type is commonly limited to smaller workpieces and to fewer stations. There is no flexibility in the design of the rotary configuration. The rotary configuration usually involves a lower-cost piece of equipment and typically requires less factory floor space. The in-line design is preferable for larger work pieces and can accommodate a larger number of workstations. In-line machines can be fabricated with a built-in storage capability to smooth out the effect of work stoppages at individual stations and other irregularities.

Source: KumarAnil, Suresh N. (2009), Production and operations management, New Age International Pvt Ltd; 2nd Ed. edition.